Combined mixed-cell and raceway aquaculture device, system and method of use thereof, and method for growing fish thereby

ABSTRACT

An energy efficient aquaculture system combining mixed-cell and raceway configurations. The system comprises a raceway tank, a raceway channel, a first water purification subsystem, and a second water purification subsystem. The system may include one or more of a hatching subsystem, a nursery subsystem, a feeding subsystem, a finishing subsystem, and a fish pumping system for transfer of fish between raceway tanks. A method of growing fish for commercial production using the aquaculture system is also provided.

The present application claims priority to U.S. Provisional ApplicationNo. 62,846,861 filed on May 13, 2019, which is incorporated herein byreference in its entirety.

FIELD OF THE TECHNOLOGY

Aspects of the present disclosure relate to a mixed-cell racewayaquaculture device, system, and methods of use thereof, and inparticular, to aspects relating to increasing the efficiency of fishproduction using a raceway.

BACKGROUND

Rearing fish by aquaculture requires the ability to effectively removefrom the water materials, such as uneaten feed or fecal matter.Consequences of a failure to remove this material include secondaryproduction of ammonia, an increase in oxygen demand, and the developmentof suspended solids in concentrations that predispose fish to bacterialgill disease and other infections (see Watten B J et al., AquaculturalEngineering 24 (2000) 59-73). Linear raceways require water exchange athigh rates making it imperative to reuse water. However, reuse isassociated with disease transmission and formation of a gradient indissolved oxygen and fish metabolites along the axis of the rearing unit(see Watten et al., 2000), resulting in increased fish mortality.Attempts to overcome these problems have included use of circular tanks,which allows for good self-cleaning and maintenance of optimalvelocities for fish health and conditioning, leading to improved growthrates and food conversion efficiencies (Timmons, M B et al., Aquacult.Eng. 18 (1998) 51-69; Davidson, J. and Summerfelt, S. T., Aquacult. Eng.32 (2004) 245-271; Labatut R A et al., Aquacultural Engineering 37(2007) 132-143). Further improvements of the related art led to araceway design in which linear raceways were modified to establish mixedflow reactor behavior (Watten et al., 2000). This design is known as themixed-cell-raceway (MCR) and it combines the advantages of circulartanks and linear raceways, e.g., uniform water quality, rapid solidsremoval, and easier husbandry and maintenance in a single vessel design.The MCR design included vertical discharge manifolds along the sidewallsof the raceways converting linear raceways into a series ofhydraulically independent mixed-cells. Each cell had a bottom-centerdrain that forced each cell to behave as an individual circular tank anda rotating hydraulic flow in a direction opposite to that of theadjacent cell.

SUMMARY

Notwithstanding the better designed MCR of the related art, thereremains a need for improved methods for rearing fish, particularly withregard to increasing energy efficiency and cost effectiveness.

Aspects of the present disclosure provide an energy efficient mixed-cellraceway device, system, and methods of use thereof for rearing fish. Insuch device, system, and method, water may flow in and flow out throughthe two ends at the longitudinal extremities of the raceway tank andalso through suitably placed drains at the bottom of the raceway, forexample. This approach, among other advantages, leads to higher fishyield per unit of energy consumed relative to previous aquaculturesystems.

Accordingly, in one aspect, the technology provides an aquaculturedevice, system, and method of use combining mixed-cell and racewayconfigurations. An example system in accordance with aspects of thepresent disclosure includes a raceway tank, a raceway channel, a firstwater purification subsystem, and a second water purification subsystem.The raceway tank may be configured as an elongated tank divided into aplurality of virtual circularly cross-sectionally shaped cells disposedalong a longitudinal axis of the tank. The tank may have a first end anda second end disposed at opposite ends of the tank along thelongitudinal axis. Further, the tank may be configured so that waterenters the tank via flow thereof being directed via a first weir at thefirst end and flows under gravity toward the second end. A first portionof the water may exit through flow thereof being directed via a secondweir at the second end and enter the first water purification subsystem.The tank may include a drain disposed at a center of each of theplurality of virtual cells. A second portion of the water may exitthrough the drains and enter the second water purification subsystem.Purified water from the first water purification subsystem may be liftedand enter the raceway channel, from which it may be gravity fed throughthe raceway channel, for example, and returned to the raceway tank viaflow thereof being directed via the first weir. The purified water fromthe second water purification subsystem may be pumped through aplurality of discharge manifolds disposed along sidewalls of the tank soas to create a rotating hydraulic flow pattern in each of the virtualcells. The hydraulic flow patterns of adjacent virtual cells mayinclude, for example, flows in at least partially opposing directions.

The aquaculture systems may have, for example, one or more of thefollowing features. The raceway tank may have one or more moving bedbioreactors at the second end of the tank. The first and/or second waterpurification subsystem also may include one or more moving bed biofilmreactors (MBBRs). The first water purification subsystem may have afirst filter for removal of solid material and the second waterpurification subsystem may have a second filter for removal of solidmaterial. The system may further include a first pump for lifting waterexiting the first water purification subsystem to a height of anentrance to the raceway channel. This pump may be a propeller-drivenpump or be or include an airlift pump, for example, and be capable oflifting water to a height of about 25 cm to about 60 cm, or about 30 cmto about 60 cm, or about 45 cm to about 60 cm and be capable ofproviding a flow of about 12,500 gallons per minute per pump, forexample. For example, the first pump may be capable of lifting 12,500gallons of water per minute at 60 cm head while consuming 11 kW ofpower. Alternatively, an airlift subsystem may be used as the firstpump; an airlift pump may use about 33% less energy than apropeller-driven pump and cost about 25% less. If greater flow capacityis needed, one or more first and/or second pumps may be added to thesystem. The second water purification subsystem may include a vacuum airlift. The subsystems may further include one or more surface aeratorsconfigured for degassing and oxygenating water in the raceway channel,which aerators may be located in the first water purification subsystemand/or in the second water purification subsystem. The systems mayfurther include an oxygen supersaturation unit for enriching dissolvedoxygen levels. The raceway tank may include 2-10 virtual cells. Thesystems may include two or more raceway tanks that are either (1)connected in parallel at their first ends to a single raceway channel,connected in parallel at their second ends to a single first waterpurification subsystem, and/or connected in parallel through theirdrains to a single second water purification subsystem; and/or (2)connected in parallel at their second ends to a single raceway channel,connected in parallel at their first ends to a single first waterpurification subsystem, and connected in parallel through their drainsto a single second water purification subsystem. The system may include,for example, 2, 3, 4, 6, 8, 10, 12, 4-8, 6-10, 8-10, or 8-12 racewaytanks. The width to depth ratio of the tank may preferably be in therange of about 3:1 to about 4:1, for example. The length of the tank maypreferably be approximately an integer multiple of the width, with theinteger corresponding to the number of virtual cells in the tank. Forexample, if the tank is 24 feet wide, it may have length of multiples of24 feet, depending on the number of virtual cells. The system mayfurther include one or more of a hatching subsystem, a nurserysubsystem, and/or a finishing subsystem. In an example implementation ofeither of the above described systems, a feeding subsystem may be added.In an embodiment of such a system, a fish pumping feature for transferof fish among raceway tanks may be added. Either of the systems may beenclosed in a single building. In one example implementation, the totalenergy consumption of either one of the systems may be in the range ofabout 2.3 kWh/kg fish to about 3.3 kWh/kg fish. In an exampleimplementation, the turnover rate of each raceway tank may be about 30minutes to about 40 minutes. In an example implementation, one or morebarriers disposed across the width of the tank may be added to thesystem, such that each barrier separates adjacent virtual cells that thebarrier falls between and prevents light but not water from passingtherethrough, thereby allowing a selected photoperiod regime to besufficiently implemented, for example, in a section defined by twobarriers and/or in a section defined by a barrier and a wall at a firstor the second end of a tank.

In one example implementation, the raceway tank comprises two barriersdefining a section that includes one or more virtual cells locatedbetween the two barriers. In another example implementation, the racewaytank comprises a barrier and an end wall together defining a sectioncomprising one or more virtual cells located therebetween.

In another aspect, the technology described herein may provide a methodof growing fish for commercial production via an aquaculture system, theaquaculture system including two or more raceway tanks, a first waterpurification subsystem, a second water purification subsystem, and oneor more finishing tanks. The method may include (a) introducing juvenilefish into a first raceway tank and allowing the fish to grow; (b)removing the fish once they have grown to a desired size or weight andtransferring the fish to one or more unoccupied raceway tanks of thesystem; (c) optionally repeating step (b) one or more times; (d)removing the fish to one or more finishing tanks after they have reacheda desired size or weight and purging the fish; and (e) harvesting thefish.

This method may alternatively or additionally include one or more of thefollowing features. The method may further include, prior to step (a):providing a nursery subsystem comprising one or more circularcross-sectionally shaped single- or dual-drain tanks; and growingfingerlings into juvenile fish in the dual-drain tanks prior to transferof the juvenile fish in step (a). In addition, the method may furtherinclude providing a hatchery subsystem comprising one or more tanks; andincubating fish eggs in the tanks and allowing the eggs to develop intofingerlings.

The method may include various features and/or steps such thatessentially all of the water used in the system may be recycled afterpurification in the first and second water purification subsystems.Further, the water in the one or more raceway tanks may be exchangedevery 20-40 minutes, for example. The method may include variousfeatures and/or steps such that when the system includes two or moreraceway tanks, the quality of water entering all raceway tanks may beessentially the same or comparable at all times.

In another aspect, the devices, systems, and methods described hereinmay include a subsystem for water purification. This subsystem maycomprise one or more filters for removing solid material, one or morepumps for lifting water, one or more surface aerators for exchange ofgas dissolved in the water, and optionally one or more MBBRs, forexample. The one or more pumps may lift water to a desired height eitherbefore or after the water has passed through the filter. The one or moresurface aerators may degas the water after it has passed through thefilter and optionally after it has passed through one or more MBBRs. TheMBBRs may contact the water either before the water has passed throughthe filter but before the water contacts the one or more surfaceaerators, for example. The one or more pumps may be or include apropeller-driven pump and/or an airlift pump.

Aspects of the present disclosure may provide another subsystem forwater purification. This subsystem may comprise one or more filters forremoving solid material, a vacuum airlift, one or more surface aeratorsfor exchange of gas dissolved in the water, and optionally one or moreMBBRs. The one or more MBBRs may contact the water either before orafter the water has passed through the filter but before the watercontacts the one or more aerators, for example. The one or more surfaceaerators may degas the water after it has passed through the filter andoptionally after it has passed through the one or more MBBRs, forexample. The vacuum air lift may remove suspended particles with sizesin the range of about 0.3 μm to about 100 μm that have passed throughthe filter.

Additional advantages and novel features of these aspects will be setforth in part in the description that follows, and in part will becomemore apparent to those skilled in the art upon examination of thefollowing or upon learning by practice of the disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of an embodiment of the aquaculture systemin accordance with aspects of the present disclosure.

FIG. 2 shows an example tank having two barriers located therein, inaccordance with aspects of the present disclosure.

FIG. 3A shows various features of an example barrier/photon deflectorfor use in a raceway tank of an example aquaculture system in accordancewith aspects of the present disclosure, and FIG. 3B shows a secondexample barrier/photon deflector for use in accordance with aspects ofthe present disclosure.

FIG. 4 is a flowchart showing a process of flow of water within anexample aquaculture system in accordance with aspects of the presentdisclosure.

FIG. 5 is a flowchart depicting elements of a process of growing fishusing an example aquaculture system in accordance with aspects of thepresent disclosure.

DETAILED DESCRIPTION

An example aquaculture system in accordance with aspects of the presentdisclosure may include features combining mixed-cell and racewayconfigurations. The system may be more energy efficient compared toexisting aquaculture systems. In this design, the bulk of water in thesystem may flow along the length of one or more individual racewayunits, also interchangeably referred to herein as raceway tanks, such asin a laminar flow pattern. Water may enter one end of the tank and thebulk of the water may exit at another point, such as an opposite end,while the remaining water may exit through drains situated at the floorof the raceway tank. The drains may serve as center points of one ormore additional, circular cross-sectional flow patterns within theoverall laminar flow pattern of each raceway tank. Water exiting theraceway tanks may be purified before being introducing back into thetanks. In some example implementations, the water exiting the racewaytank may be lifted to a suitable height either before or after passingthrough the purification unit, such that the reintroduction of the waterinto the raceway tank may be performed efficiently under gravity. Beforechanneling the exited water back into the raceway tank, some or all ofsuch exited water may be aerated to remove CO₂ and replenish oxygen.Water exiting the raceway tank through the drains may be collected inpipes and flow under gravity to an area where it may be purified andsupersaturated with oxygen. This water may be reintroduced into theraceway tank, for example, through submerged jets.

An example implementation of various features of an aquaculture systemin accordance with aspects of the present disclosure is depicted inFIG. 1. The system 100 shown in FIG. 1 includes several raceway tanks101, a raceway channel 102 for return of water to the tanks 101, such asafter purification, a first water purification subsystem 103, a racewaychannel 112 for conveying water exiting the raceway tanks to the firstwater purification subsystem 103, and a second water purificationsubsystem 104. Each raceway tank 101 may have an elongated overallcross-sectional area that encompasses one or more virtual cells 105disposed along a longitudinal axis of the tank 101. Each tank 101 mayhave a first end 106 and a second end 107 disposed at opposite ends ofthe tank 101 along its longitudinal axial direction. Each tank 101 maybe configured so that water enters the tank 101, for example, via afirst weir 108 that communicates flow thereof with the first end 106 ofthe tank 101 and flows (e.g., via the action of gravity) toward thesecond end 107 of the tank 101. A portion of the water may exit the tankat the second end 107 via communication of flow thereof via a secondweir 109 and flow through raceway channel 112 so as to enter the firstwater purification subsystem 103. This flow of water, prior to exitingvia flow directed via the second weir 109 and entering the first waterpurification subsystem 103, may come into contact with one or more MBBRs114. Microorganisms present in the bioreactors 114 may consume organicmaterial present in the water and help purify the water. The floor ofeach tank 101 may have several drains 111 located therein, one of thedrains 111 being disposed at the center of each of the of virtual cells105, for example. The system 100 depicted in FIG. 1 shows an example ofcylindrically shaped flows illustrated by pairs of circularcross-sectionally shaped arrows within five virtual cells per racewaytank 101, but each raceway tank may contain two or more, three or more,four or more, five or more, or from two to ten virtual such cells. Asecond portion of the water may exit the tank 101 via the drains 111 andbe communicated to the second water purification subsystem 104.

Purified water from the first water purification subsystem 103 may belifted and enter the raceway channel 102, from which the water may thenbe communicated (e.g., via gravity feed) via the raceway channel 102back to the raceway tank 101 via the first weir 108. The purified waterfrom the second water purification subsystem 104 may be pumped throughmultiple discharge manifolds 113, for example, disposed along thesidewalls of each tank 101 so as to produce a rotating hydraulic flowpattern in each of the virtual cells, the hydraulic flow patterns ofadjacent virtual cells having at least components of their flow patternsextending in opposite directions to one another (e.g., at outer edges offlows where proximal to one another).

Raceway channels 102 and 112 may be open, i.e., the water flowing in thechannel may be exposed to atmosphere, or alternately closed, such as bybeing contained within a flow conveying pipe or culvert.

In some embodiments adjacent raceway tanks 101 of the aquaculture system100 may be separated from one another so as to form a passagetherebetween that may be accessible by workers, for example, such aswhen tending to fish in the tanks 101 or when tending to the care of thetanks 101 themselves.

The first water purification subsystem 103 may comprise a first filter115 for removal of solid material, and the second water purificationsubsystem 104 may include a second filter 116 for removal of solidmaterial, for example. A first pump 117 may lift, for example, waterexiting the first water purification subsystem 103 to a sufficientheight such that the flow of water may communicate with an entrance tothe raceway channel 102. The second water purification subsystem 104 mayfurther comprise a vacuum air lift 118, for example.

The system 101 may further includes one or more surface aerators 119configured for degassing and oxygenating water contained in the racewaychannel 102, in the first water purification subsystem 103, and/or inthe second water purification subsystem 104. Another pump, e.g., acentrifugal pump (not shown in FIG. 1), or other flow directing device,may be used to deliver the water leaving the second purificationsubsystem 104 to an oxygen supersaturation unit 120, for example. Oxygensupersaturated water may then exit the unit 120 and be delivered to thetanks 101, such as via through the manifolds 113.

The system 100 may also include a hatching subsystem 121, nurserysubsystem 122, and/or finishing subsystem 123.

The first water purification subsystem 103 may include a filter 115 forremoval of solid materials, such as a rotary vacuum drum filter (RVDF)that may effectively remove suspended solid material (e.g., fish fecalmatter and/or uneaten feed). Multiple RVDFs may be used, depending uponthe volume of water to be filtered. The pumps 117 in the subsystem 103may lift the water either before or after purification. The pump orpumps 117 may be or include one or more propeller driven pumps, forexample. An example propeller driven pump suitable for use in the systemis a pump sold by AgriMarine Technologies Inc. (ATI), Canada, which maylift 12,500 gpm of water up to 60 cm using only 11 kWh. Alternatively,pump 117 may be an airlift pump, for example. The airlift pump mayinject compressed air at the bottom of a discharge pipe immersed in thewater. The compressed air may then mix with the water, causing thelighter air-water mixture to rise upwards. An airlift pump may generallyhave the advantage of being more energy-efficient and less capitalintensive than other types of pumps, for example.

The second purification subsystem 104 may include a filter 116 forremoval of solid materials. Water purified in this subsystem may includewater exiting the drains 111 in each raceway tank 101, the bottom flowof which may be directed via pipes and flow thereof, such as may becaused by gravity, for example, to subsystem 104. As with the firstpurification subsystem 103, filter 116 in subsystem 104 also may be orinclude a RVDF. Subsystem 104 may include a vacuum air lift 118 forseparating suspended solids or liquids from the water. The vacuumairlift 118 may assist in extraction of particles having a size of about0.3 μm to about 100 μm and also other substances, such as oil andhydrocarbons. A vacuum airlift 118 generally operates by raising waterin a column using vacuum, which may cause the water to bubble. Thebubbles may trap the particles and appear in the form of foam at the topof the water column. The foam may then be removed and the processrepeated. The use of vacuum airlift may also lead to stripping of CO₂.Subsystem 104 may also include one or more MBBRs 114 for removal of gas,such as ammonia, as well as one or more surface aerators 119.

The system may further include an oxygen supersaturation unit or anoxygen contactor unit 120 for oxygenating water exiting the secondpurification subsystem 104 before it is introduced into the raceway tank101. Generally, an oxygen contactor includes a closed cylinder throughwhich water is passed while being contacted with oxygen applied at apressure. A high degree of saturation, e.g., up to 700%, may be achievedat medium pressures, e.g., 1.5 bar. An example oxygenator that may beused in the system described herein is the Oxyflow®, made by AquacareEnvironment, Inc., of Bellingham, Wash., which is a low head oxygenatorthat operates in a sealed vessel, thus not breaking head pressure. Watermay enter the top of the unit under mild pressure of about 0.3 bar. Thewater may next pass through a horizontal drilled plate with speciallyshaped orifice holes (number and size determined by flow rate required)which may jet the water downward though an oxygen atmosphereapproximately 20 cm depth. When the jets strike the water surface below,they may cause a high turbulence and create a bubble cloud of pureoxygen that extends downwards to 40 cm below the surface of the water.These buoyant bubbles flow upwards, counter to the downward water flow,in such a way that the downward velocity is not strong enough to carrythe bubbles out of the chamber, hence the only way the oxygen gas mayescape the OxyFlow® unit is upon becoming dissolved in the water.Bubbles that break the water surface inside the unit may again besubjected to the turbulence of the downward jets until they becomedissolved. A small amount of nitrogen gas that remains in the oxygenrich atmosphere may be vented off to prevent it from becoming dissolvedin the water. In this manner, gaseous oxygen may be converted intodissolved oxygen in a reliable and cost-effective way.

The pressure the water is under in the oxygen supersaturation unit 120may force the water through the jets in the submerged manifolds 113. Asmentioned above, water may be delivered to the to oxygen supersaturationunit 120 by means of a pump, e.g., a centrifugal pump (not shown in FIG.1).

In one embodiment, about 50%-80% of the water entering the raceway tank101 at the first end 106 may exit through the second end 107, and about20%-50% of the water may exit through the drains 111 at the bottom ofthe tank 101. In another embodiment, about 70% of the water entering theraceway tank 101 at the first end 106 may exit through the second end107, and about 20%-50% of the water may exit through the drains 111.

The ratio of the width to the depth of the raceway tank 101 may varybetween about 3:1 to about 4:1. The length of the raceway tank 101 maybe about 40 feet to about 200 feet long.

As shown in FIG. 2, one or more of the raceway tanks 101 may furtherinclude one or more barriers 210 disposed across the width of the tank101, and each barrier 210 may separates adjacent virtual circular cells(as shown in FIG. 1) and prevent light but not water from passingtherethrough, thereby allowing, for example, a particular photoperiodregime to be implemented in a section defined by two barriers or by abarrier and either the wall defining the first or the second end. Thebarriers may also be interchangeably referred to herein as photondeflectors.

Photoperiod plays an especially important role in the rearing of aterminal spawning fish, such as Coho salmon. To achieve maximum growthand delay maturation, the fish need to experience a rigid photoperiodregime. For example, if the fry are not smolted, the entire growingperiod may be disrupted, resulting in poor growth and erratic maturity.There are three distinct photoperiod (PP) regimes, namely, smolting,growth spurt, and maturing. An example of a photoperiod protocol appliedfrom first feeding to smolting, and finally from the growth spurt(overwintering) to market is shown in the Table below.

TABLE Photoperiod (approximate timelines) eyed eggs 1^(st) feeding 5grams- 30-700 700-1200 1.2 kilos- and alevins fry - 5 grams 30 gramsgrams grams market 0:24 16:8 24:0 16:8 8:16 24:0 L:D L:D L:D L:D L:D L:D6 12 40 46 64 weeks weeks weeks weeks weeks PFF PFF PFF PFF PFF PFF—postfirst feeding, L:D (light:darkness)

By utilizing the barrier or the photon deflector, the raceway may bedivided along the circular cells, enabling more efficient utilization ofthe growing space. As the fish grow, the deflector may be moved alongthe raceway to bring an increasing number of cells under use, therebyenabling utilization the cells to their full potential and increasingthe efficiency of the raceway.

In one embodiment, the aquaculture system may comprise twobarriers/photon deflectors defining a section comprising one or morevirtual cells between the two barriers (FIG. 3A). Varying designs may beused to construct the photon deflectors. For example, the photondeflector may have angled slats or opposing chevrons as shown in FIG.3B.

In another example implementation, the aquaculture system may compriseone barrier defining a section comprising one or more virtual cellslocated between the barrier and a wall of the tank at the first end orthe second end.

A flowchart of an example process for flow of water through anaquaculture system along the lines discussed above is shown in FIG. 4.Water enters the raceway tank from the first raceway channel at one endof the tank (400). A portion of this water flows through the tank andexits via drains at the floor of the tank (401). This water enters thesecond water purification subsystem where it is filtered, biofiltered(using MBBR), and aerated (402). The filtered and aerated water entersthe oxygen supersaturation unit (403). Next, the oxygen supersaturatedwater is pumped to discharge manifolds at the sidewalls of the tank(404). Another portion of the water entering the raceway tank (400)flows through the tank and MBBR, and exits via a weir at the second endof the tank (405). This water enters the second raceway channel (406).Water flows through the second raceway channel and enters the firstwater purification subsystem where it is filtered and aerated (407).This filtered and aerated water enters the first raceway channel andflows toward the raceway tank (408) to enter the tank again (400).

A flowchart of an example process for growing fish using an exampleaquaculture system along the lines discussed above is shown in FIG. 5.Initially, fish eggs are incubated and allowed to develop intofingerlings (501). Fingerlings are allowed to grow into juvenile fish inthe dual-drain tanks (502). Next, the juvenile fish are introduced intoa raceway tank and allowed to grow (503). Thereafter, once sufficientlygrown, the fish are transferred to one or more unoccupied raceway tanks,and this portion of the process is repeated, as necessary (504). Next,once desired size/weight is reached, the fish are transferred tofinishing tanks (505). Finally, the fish are purged and harvested (506).

Other Alternatives

For the convenience of the reader, the above description has focused ona representative sample of all possible embodiments, a sample thatteaches the principles of the present disclosure and conveys the bestmode contemplated for carrying it out. The description has not attemptedto exhaustively enumerate all possible variations. Other undescribedvariations or modifications may be possible. Where multiple alternativeembodiments are described, in many cases it will be possible to combineelements of different embodiments, or to combine elements of theembodiments described here with other modifications or variations thatare not expressly described. A list of items does not imply that any orall of the items are mutually exclusive, nor that any or all of theitems are comprehensive of any category, unless expressly specifiedotherwise. In many cases, one feature or group of features may be usedseparately from the entire apparatus or methods described. Many of thoseundescribed variations, modifications and variations are within theliteral scope of the following claims, and others are equivalent.

1. An aquaculture system, comprising: at least a first raceway tank,wherein the first raceway tank includes: an elongated tank body havingsidewalls, the sidewalls having a plurality of discharge manifoldsdisposed therein, the tank being divided into a plurality of virtualcells, each of the virtual cells being disposed along a longitudinalaxis of the tank, wherein each of the discharge manifolds communicateswith one of the plurality of virtual cells, wherein the tank has a firstend and a second end disposed at opposite ends of the tank along thelongitudinal axis; wherein the tank is configured such that water entersthe tank via a first weir communicating flow thereof with the first endof the tank, and wherein the water flows within the tank toward thesecond end; wherein a first portion of the water in the tank exits thetank at the second end via communication of flow thereof with a secondweir located proximal to the second end of the tank; wherein the tankcomprises a plurality of drains, each of the plurality of drains beingdisposed at a center of one of the plurality of virtual cells, andwherein a second portion of the water in the tank exits the tank via theplurality of drains; a first water purification subsystem, wherein waterreceived via the communication of flow thereof by the second weir iscommunicated to the first water purification subsystem; a second waterpurification subsystem, wherein the second portion of the water exitingthe tank via the plurality of drains is communicated to the second waterpurification subsystem, and wherein the water received by the secondwater purification system exits the second water purification system viacommunication with the plurality of discharge manifolds of the tank soas to produce a generally circular cross-sectionally shaped hydraulicflow pattern in each of the virtual cells, the hydraulic flow patternsof adjacent virtual cells having at least components of the flowpatterns extending in opposite directions to one another; a firstraceway channel, wherein the water received by the first waterpurification subsystem is communicated via the first raceway channel tothe raceway tank via the first weir; and a second raceway channel,wherein the water exiting the tank at the second end is communicated tothe first water purification subsystem via the second raceway channel.2. The aquaculture system of claim 1, further comprising one or moremoving bed reactors located proximal to the second end of the racewaytank
 3. The system of claim 1, wherein the tank is configured such thatthe water flows from the first end to the second end under action ofgravity.
 4. The system of claim 1, wherein purified water from the firstwater purification subsystem is lifted and enters the raceway channel,from which the purified water is fed through the raceway channel andreturned to the raceway tank through direction of flow thereof via thefirst weir.
 5. The system of claim 1, wherein the first or second waterpurification subsystem comprises one or more moving bed reactors.
 6. Thesystem of claim 1, wherein the first water purification subsystemcomprises a first filter for removal of solid material and the secondwater purification subsystem comprises a second filter for removal ofsolid material.
 7. The system of claim 1, further comprising: a firstpump for lifting purified water exiting the first water purificationsubsystem to a height of an entrance to the raceway channel.
 8. Thesystem of claim 7, wherein the first pump comprises a propeller drivenpump or an airlift pump.
 9. The system of claim 7, wherein the firstpump is capable of lifting the purified water to a height of about 25 cmto about 60 cm.
 10. The system of claim 1, wherein the second waterpurification subsystem further comprises a vacuum air lift.
 11. Thesystem of claim 1, further comprising: one or more surface aeratorsconfigured for degassing and oxygenating water in the raceway channel,or in the first water purification subsystem, or in the second waterpurification subsystem.
 12. The system of claim 1, further comprising:an oxygen supersaturation unit for enriching dissolved oxygen levels forwater communicated with the first tank.
 13. The system of claim 1,wherein the raceway tank comprises 2-10 of the virtual cells.
 14. Thesystem of claim 1, further comprising at least a second raceway tankthat is oriented in a parallel direction relative the first raceway tanksuch that the first ends of each of the first and second raceway tanksare each proximal to the first raceway channel, and such that the secondsecond ends of each of the first and second raceway tanks are proximalto a second raceway travel that is configured to communicate flow ofwater received therein to the first water purification subsystem, andwherein the plurality of drains for the first and second raceways eachcommunicate flow of water thereinto with the second water purificationsubsystem.
 15. The system of claim 14, further comprising at least sixadditional raceway tanks.
 16. The system of claim 1, further comprising:one or more of a hatching subsystem, a nursery subsystem, and afinishing subsystem each in fluid communication with the tank.
 17. Thesystem of claim 1, further comprising: a feeding subsystem in fluidcommunication with the tank.
 18. The system of claim 1, furthercomprising: a fish pumping system for transfer of fish with the tank.19. The system of claim 1, wherein the system is enclosed in a singlebuilding.
 20. The system of claim 1, wherein the system is capable ofproducing fish at a total energy consumption in the range of about 2.3kilowatt-hour/kg fish to about 3.3 kilowatt-hour/kg fish. 21-29.(canceled)
 30. An aquaculture system of claim 1, further comprising oneor more barriers disposed across the width of the tank, wherein eachbarrier separates adjacent virtual cells and prevents light but notwater from going through, thereby allowing a particular photoperiodregime to be implemented in a section defined by two barriers or abarrier and either the wall defining the first or the second end. 31.The aquaculture system of claim 30, comprising two barriers defining asection comprising one or more virtual cells between the two barriers.32. The aquaculture system of claim 30, comprising one barrier defininga section comprising one or more virtual cells between the barrier andthe wall at the first end or the second end.